The purpose of the investigation is to determine whether the risk of transfusion-acquired cytomegalovirus (CMV) infections in premature infants can be decreased by the use of donors who have no measurable antibody to CMV and to evaluate the most practical assay for use by a blood bank. Host factors which influence the severity of the disease in the baby are being evaluated. Severe infections have been identified in infants of seronegative mothers. Surviving infected infants are being studied in comparison with controls for the possibility that prenatally acquired CMV infections result in long term sequelae in premature infants. Tests of vision, hearing and intellectual function are being performed at 1, 2 and 3 years of age. Current studies are aimed at identifying the reasons for the failure of infected infants to respond to CMV antigen in the lymphocyte transformation assay. The transmission of CMV from infected baby to seronegative household contacts is being investigated in an effort to evaluate the risk of transmission from infected infants to seronegative mothers during a subsequent pregnancy.